1. Field of the Invention
The present invention relates to an apparatus and a method for producing a resin product which includes an inner layer and an outer layer, and, more particularly, to an apparatus and a method for producing a resin product in which part of an inner layer (a first resin layer) is covered with an outer layer (a second resin layer) so that a boundary line between the inner layer and the outer layer is visible from the outside.
2. Description of Related Art
Recently, various attempts are being made to improve the esthetic appearance and tactile impression of a resin product by covering a partial area of a surface of the resin product with an outer layer which is comprised of material different from that of the resin product. In an exemplary automotive crash pad, as shown in FIG. 1, an outer layer, which has a material (in particular, a soft material unlike that of the crash pad) and a color, different from that of the crash pad 1, is formed on a door region 2 of a passenger air bag (“PAB”) so as to give off a feeling of sophistication.
As shown in FIG. 2, such a conventional crash pad has been generally manufactured in a manner in which an outer component, which is separately produced in advance, is attached to the crash pad 1. These days, a recent technical development is to realize a PAB door region 2 which is integrally covered with an outer layer of material different from that of the PAB door at the time of the injection molding process of a crash pad. As compared with the former process which requires two different molds and processes of assembly of the outer component, the latter method is relatively advantageous in that it is excellent in terms of cost and the appearance of a fabricated crash pad, in particular, the boundary line of the PAB door region 2 is clean-cut and clearly demarcated.
Referring to FIGS. 3A to 3E, a process of producing a crash pad through the latter method will be described below.
An apparatus for producing the crash pad comprises a mold, and a first resin supply unit 10 and a second resin supply unit 20 for supplying resin material into an internal space in a mold. The mold comprises a first mold side having a recess 30, a second mold side, and a slide core movably fitted in the recess 30 of the first mold side. In such a crash pad, PPF resin (Polypropylene Filled Resin) such as talc-filled polypropylene resin is used as a first resin material, and flexible TPO resin (Thermoplastic Olefin Resin) is used as a second resin material.
The process of producing the crash pad is conducted in a manner that the slide core is moved to the extracted position to define a first cavity 11 (FIG. 3A), the first resin is supplied into the first cavity 11 to form a first resin layer 1a (FIG. 3B), the slide core is moved to the retracted position to define a second cavity 21 (FIG. 3C), and prior to the solidification of the first resin, second resin is supplied into the second cavity 21 to form a second resin layer 2a on the first resin layer 1a (FIG. 3D). The resulting crash pad, which is produced in this manner, has a considerably well delimited boundary line B between the first and second resin layers 1a and 2a (FIG. 3E).
However, the above apparatus and method for producing a crash pad has the following disadvantages.
As shown in FIG. 4, since the second resin (PPF) is injected before the complete solidification of the first resin (TPO), there may be a gap between the first and second mold sides, so that the second resin leaks into the zone of the first resin through the gap, thus hindering the clean-cut appearance at the boundary line.
Furthermore, as shown in FIG. 5, the rear surface of the resulting crash pad is post-processed to produce a tear line L, and is attached to a chute 3 of an airbag module in a fusion manner. The chute 3 is assembled with a housing 4 which accommodates a folded cushion 5. Unfortunately, such a post-processing formation of the tear line L increases production costs of the crash pads, and a degree of freedom of the post-process is not so high. Furthermore, when the processing accuracy is lowered, there may be a fear that the breaking strength at the tear line L is excessively increased.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.